The recently introduced approximate entropy statistic (ApEn) has revealed striking differences in the profiles of secretion of LH and FSH in sheep and, based on a pilot study of five subjects, in women with FSH appearing to be secreted in a far more irregular fashion than LH. This Small Business Innovative Research grant from the NIH will extend the pilot study in women by providing funding to study changing profiles of LH and FSH in an additional five women. This involves obtaining samples of blood every 7.5 min for 24 hrs from five women during days 2-5 of the follicular phase of their cycle and again, after a month with no sampling, from the mid-luteal phase. The study will provide a far better baseline of information that can serve as a reference for future studies comparing differences in relative regularity of the secretion of these gonadotropins in women in other stages of life or with other conditions, e.g. perimenopausal, post-menopausal, with polycystic ovarian syndrome, with short luteal phase defect, and with other reproductive states. The ApEn statistic provides completely different information complementing that obtained by conventional techniques of pulse analysis.